Off-the-clot (OTC) serum is produced by allowing whole blood to coagulate naturally \u2014 without the addition of anticoagulants \u2014 and then centrifuging the clotted sample to separate the liquid serum fraction. This method preserves the natural complement cascade and yields serum with a full protein profile, including all coagulation factors consumed during clotting.<\/p>\n
Plasma is produced by centrifuging anticoagulated blood, retaining fibrinogen and coagulation factors. Serum is produced after clotting, so these factors are absent. The key practical difference: serum will not clot when added to cell cultures or assay systems. Plasma contains fibrinogen that may form fibrin strands under certain conditions.<\/p>\n
In IVD assay development, the serum matrix must closely replicate the composition of patient diagnostic samples \u2014 which are typically serum collected OTC. Using OTC human serum as the matrix for calibrators and controls ensures matrix-matched performance and accurate clinical correlation.<\/p>\n
OTC human serum is used in T cell and PBMC culture as a supplement, in IVD calibrator and control matrix production, and in immunology and serology research.<\/p>\n